Associations between Vegetable Nitrate Intake and Cardiovascular Disease Risk and Mortality: A Systematic Review

Consumption of nitrate-rich vegetables increases nitric oxide bioavailability, lowers blood pressure, and improves endothelial function. These effects could also translate into reduced cardiovascular disease (CVD) risk and mortality. This systematic review aimed to investigate the associations between habitual vegetable nitrate intake and CVD incidence and mortality. A secondary aim was to identify factors that moderate the relationship between vegetable nitrate intake and CVD incidence/mortality. Seven databases (PubMed, MEDLINE, Embase, Scopus, Web of Science, CINAHL, and APA PsycINFO) were searched from inception to 13 February 2023. Observational studies quantifying vegetable nitrate intake in participants aged 18+ years through self-reported dietary exposure and assessing incidence or mortality from CVD overall, or individual CVD subtypes, were eligible. Five studies including a total of 63,155 participants were included. There was an inverse association between vegetable nitrate intake and most reported CVD outcomes. Reported risk reductions tended to plateau at moderate intake, suggesting a possible ceiling effect. The risk of bias across all studies was low. The results of this systematic review suggest a potential role for vegetable nitrate in reducing CVD risk and mortality. Further randomised controlled trials are now required to corroborate these findings.

Effects of dietary nitrate supplementation on oral health and associated markers of systemic health: a systematic review

Poor oral health can impact an individual's ability to eat and has been associated with an increased risk of non-communicable diseases. While the benefits of nitrate consumption on oral health were first proposed more than 20 years ago, no systematic review has been published examining effects of dietary nitrate on oral health. This systematic review investigated the effects of dietary nitrate on markers of oral health in vivo in randomized controlled trials (RCTs). Five databases (PubMed, The Cochrane Library, CINAHL, MEDLINE, and SPORTDiscus) were searched from inception until March 2023. Nine articles reporting data on 284 participants were included. Dietary nitrate was provided via beetroot juice in most studies. The duration of the interventions ranged from one day to six weeks. Dietary nitrate supplementation increased the relative abundance of several individual bacterial genera including Neisseria and Rothia. Dietary nitrate supplementation increased salivary pH and decreased salivary acidification following consumption of a sugar-sweetened beverage. Furthermore, dietary nitrate supplementation resulted in a decrease in the gingival inflammation index. The results of this systematic review suggest that dietary nitrate could represent a potential nutritional strategy to positively modify oral health by impacting the oral microbiome, altering salivary pH, and minimizing gingival inflammation.

Pharmacological interventions for the management of children and adolescents living with obesity-An update of a Cochrane systematic review with meta-analyses

IMPORTANCE

The effectiveness of anti-obesity medications for children and adolescents is unclear.

OBJECTIVE

To update the evidence on the benefits and harms of anti-obesity medication.

DATA SOURCES

Cochrane CENTRAL, MEDLINE, ClinicalTrials.gov and WHO ICTRP (1/1/16-17/3/23).

STUDY SELECTION

Randomized controlled trials ≥6 months in people <19 years living with obesity.

DATA EXTRACTION AND SYNTHESIS

Screening, data extraction and quality assessment conducted in duplicate, independently.

MAIN OUTCOMES AND MEASURES

Body mass index (BMI): 95th percentile BMI, adverse events and quality of life.

RESULTS

Thirty-five trials (N = 4331), follow-up: 6-24 months; age: 8.8-16.3 years; BMI: 26.2-41.7 kg/m2. Moderate certainty evidence demonstrated a -1.71 (95% confidence interval [CI]: -2.27 to -1.14)-unit BMI reduction, ranging from -0.8 to -5.9 units between individual drugs with semaglutide producing the largest reduction of -5.88 kg/m2 (95% CI: -6.99 to -4.77, N = 201). Drug type explained ~44% of heterogeneity. Low certainty evidence demonstrated reduction in 95th percentile BMI: -11.88 percentage points (95% CI: -18.43 to -5.30, N = 668). Serious adverse events and study discontinuation due to adverse events did not differ between medications and comparators, but medication dose adjustments were higher compared to comparator (10.6% vs 1.7%; RR = 3.74 [95% CI: 1.51 to 9.26], I2 = 15%), regardless of approval status. There was a trend towards improved quality of life. Evidence gaps exist for children, psychosocial outcomes, comorbidities and weight loss maintenance.

CONCLUSIONS AND RELEVANCE

Anti-obesity medications in addition to behaviour change improve BMI but may require dose adjustment, with 1 in 100 adolescents experiencing a serious adverse event.

Adherence to the Eatwell Guide and cardiometabolic, cognitive and neuroimaging parameters: an analysis from the PREVENT dementia study

BACKGROUND

The Eatwell guide reflects the UK government's recommendations for a healthy and balanced diet. Previous research has identified associations between healthy eating patterns and both cardiovascular and brain health, although there is little evidence specifically focusing on the Eatwell Guide. To date no research has investigated associations between the Eatwell Guide and risk for future dementia.

METHODS

Data from the PREVENT dementia cohort study baseline visit was used in this analysis. Binary and graded Eatwell Guide scores (BEWG, GEWG) were created from a self-reported Food Frequency Questionnaire. The CAIDE score was included as the primary outcome measure to represent risk for future Alzheimer's disease. Secondary outcome measures included cardiometabolic health measures and brain health measures. Generalised additive models were run in R.

RESULTS

A total of 517 participants were included in the analysis, with a mean BEWG score of 4.39 (± 1.66) (out of a possible 12 points) and GEWG score of 39.88 (± 6.19) (out of a possible 60 points). There was no significant association between either Eatwell Guide score and the CAIDE score (BEWG β: 0.07, 95% confidence interval (CI): -0.07, 0.22; GEWG β: 0.02, 95% CI: -0.02, 0.06) or any measures of brain health. There was a significant association between higher GEWG score and lower systolic and diastolic blood pressure and body mass index (BMI) (systolic β: -0.24, 95% CI: -0.45, -0.03; diastolic β: -0.16, 95% CI: -0.29, -0.03; BMI β: -0.09, 95% CI: -0.16, -0.01).

CONCLUSIONS

Although not directly associated with the CAIDE score, the Eatwell Guide dietary pattern may be beneficial for dementia prevention efforts through the modification of hypertension and obesity, which are both known risk factors for dementia. Future work could replicate these findings in other UK-based cohorts as well as further development of Eatwell Guide scoring methodologies.

The Effect of High-Fat Diet on Intramyocellular Lipid Content in Healthy Adults: A Systematic Review, Meta-Analysis, and Meta-Regression

Fatty acids are stored within the muscle as intramyocellular lipids (IMCL). Some, but not all, studies indicate that following a high-fat diet (HFD), IMCL may accumulate and affect insulin sensitivity. This systematic review and meta-analysis aimed to quantify the effects of an HFD on IMCL. It also explored the potential modifying effects of HFD fat content and duration, IMCL measurement technique, physical activity status, and the associations of IMCL with insulin sensitivity. Five databases were systematically searched for studies that examined the effect of ≥3 d of HFD (>35% daily energy intake from fat) on IMCL content in healthy individuals. Meta-regressions were used to investigate associations of the HFD total fat content, duration, physical activity status, IMCL measurement technique, and insulin sensitivity with IMCL responses. Changes in IMCL content and insulin sensitivity (assessed by hyperinsulinemic-euglycemic clamp) are presented as standardized mean difference (SMD) using a random effects model with 95% confidence intervals (95% CIs). Nineteen studies were included in the systematic review and 16 in the meta-analysis. IMCL content increased following HFD (SMD = 0.63; 95% CI: 0.31, 0.94, P = 0.001). IMCL accumulation was not influenced by total fat content (P = 0.832) or duration (P = 0.844) of HFD, physical activity status (P = 0.192), or by the IMCL measurement technique (P > 0.05). Insulin sensitivity decreased following HFD (SMD = -0.34; 95% CI: -0.52, -0.16; P = 0.003), but this was not related to the increase in IMCL content following HFD (P = 0.233). Consumption of an HFD (>35% daily energy intake from fat) for ≥3 d significantly increases IMCL content in healthy individuals regardless of HFD total fat content and duration of physical activity status. All IMCL measurement techniques detected the increased IMCL content following HFD. The dissociation between changes in IMCL and insulin sensitivity suggests that other factors may drive HFD-induced impairments in insulin sensitivity in healthy individuals. This trial was registered at PROSPERO as CRD42021257984.

Can the delivery of behavioural support be improved in the NHS England Low-Calorie Diet Programme? An observational study of behaviour change techniques

BACKGROUND

Previous research has illustrated a drift in the fidelity of behaviour change techniques (BCTs) during the design of the pilot NHS England Low-Calorie Diet (NHS-LCD) Programme. This study evaluated a subsequent domain of fidelity, intervention delivery. Two research questions were addressed: (1) To what extent were BCTs delivered with fidelity to providers programme plans? (2) What were the observed barriers and facilitators to delivery?

METHODS

A mixed-methods sequential explanatory design was employed. Remote delivery of one-to-one and group-based programmes were observed. A BCT checklist was developed using the BCT Taxonomy v1; BCTs were coded as present, partially delivered, or absent during live sessions. Relational content analysis of field notes identified observed barriers and facilitators to fidelity.

RESULTS

Observations of 122 sessions across eight samples and two service providers were completed. Delivery of the complete NHS-LCD was observed for five samples. Fidelity ranged from 33% to 70% across samples and was higher for group-based delivery models (64%) compared with one-to-one models (46%). Barriers and facilitators included alignment with the programme's target behaviours and outcomes, session content, time availability and management, group-based remote delivery, and deviation from the session plan.

CONCLUSIONS

Overall, BCTs were delivered with low-to-moderate fidelity. Findings indicate a dilution in fidelity during the delivery of the NHS-LCD and variation in the fidelity of programmes delivered across England. Staff training could provide opportunities to practice the delivery of BCTs. Programme-level changes such as structured activities supported by participant materials and with sufficient allocated time, might improve the delivery of BCTs targeting self-regulation.

Adherence to the Eatwell Guide and population and planetary health: A Rank Prize Forum report

This report summarises a Forum conducted in June 2023 to explore the current state of the knowledge around the Eatwell Guide, which is the UK government's healthy eating tool, in relation to population and planetary health. The 1.5-day Forum highlighted the limited, albeit promising evidence linking higher adherence to the Eatwell Guide with favourable health outcomes, including reduced overall mortality risk, lower abdominal obesity in post-menopausal women and improved cardiometabolic health markers. Similarly, evidence was presented to suggest that higher adherence to the Eatwell Guide is associated with reduced greenhouse gas emissions. Presentations were given around cultural adaptations of the Eatwell Guide, including African Heritage and South Asian versions, which are designed to increase the acceptability and uptake of the Eatwell Guide in these communities in the United Kingdom. Presentations highlighted ongoing work relevant to the applications of the Eatwell Guide in randomised controlled trials and public health settings, including the development of a screening tool to quantify Eatwell Guide adherence. The Forum ended with a World Café-style event, in which the strengths and limitations of the Eatwell Guide were discussed, and directions for future research were identified. This Forum report serves as a primer on the current state of the knowledge on the Eatwell Guide and population and planetary health and will be of interest to researchers, healthcare professionals and public health officials.

Associations between anxiety, depression, and weight status during and after pregnancy: A systematic review and meta-analysis

Previous work has found adverse mental health symptomology in women living with obesity, compared with those of healthy weight, around the time of pregnancy. This meta-analysis aimed to explore the association between anxiety, depression, and weight status in women living with obesity before, during, and after pregnancy. Bibliographic databases were systematically searched, and 14 studies were included, which aimed to assess the association between excess weight and anxiety or depression outcomes in women before, during, or after pregnancy. Data were analyzed via narrative synthesis and random effects multi-level meta-analyses. Scores on mental health indices were significantly greater (indicative of worse anxiety/depression) in women with obesity compared to women of a healthy weight, around the time of pregnancy (SMD = 0.21 [95% CI: 0.11-0.31; 95% prediction intervals: 0.13-0.56], I2  = 73%, p < 0.01). Depressive symptoms were greater during and after pregnancy (SMD = 0.23 [95% CI: 0.13-0.34; 95% prediction intervals: -0.12 to 0.59], I2  = 75.0%, p < 0.01), and trait anxiety symptoms were greater during pregnancy (SMD = 0.24 [95% CI: 0.01-0.47; 95% prediction intervals: -0.25 to 0.72], I2  = 83.7%, p = 0.039) in women living with obesity, compared to those of healthy weight. Narrative evidence suggests that socioeconomic status and ethnicity may modify the relationship between obesity and mental health symptomology. The findings indicate that maternal obesity is associated with greater anxiety and depression symptoms. These findings may inform the design of maternal weight management interventions.

Does the design of the NHS Low-Calorie Diet Programme have fidelity to the programme specification? A documentary review of service parameters and behaviour change content in a type 2 diabetes intervention

BACKGROUND

NHS England commissioned four independent service providers to pilot low-calorie diet programmes to drive weight loss, improve glycaemia and potentially achieve remission of Type 2 Diabetes across 10 localities. Intervention fidelity might contribute to programme success. Previous research has illustrated a drift in fidelity in the design and delivery of other national diabetes programmes.

AIMS

(1) To describe and compare the programme designs across the four service providers; (2) To assess the fidelity of programme designs to the NHS England service specification.

METHODS

The NHS England service specification documents and each provider's programme design documents were double-coded for key intervention content using the Template for Intervention Description and Replication Framework and the Behaviour Change Technique (BCT) Taxonomy.

RESULTS

The four providers demonstrated fidelity to most but not all of the service parameters stipulated in the NHS England service specification. Providers included between 74% and 87% of the 23 BCTs identified in the NHS specification. Twelve of these BCTs were included by all four providers; two BCTs were consistently absent. An additional seven to 24 BCTs were included across providers.

CONCLUSIONS

A loss of fidelity for some service parameters and BCTs was identified across the provider's designs; this may have important consequences for programme delivery and thus programme outcomes. Furthermore, there was a large degree of variation between providers in the presence and dosage of additional BCTs. How these findings relate to the fidelity of programme delivery and variation in programme outcomes and experiences across providers will be examined.

Mediterranean diet adherence is associated with lower dementia risk, independent of genetic predisposition: findings from the UK Biobank prospective cohort study

BACKGROUND

The identification of effective dementia prevention strategies is a major public health priority, due to the enormous and growing societal cost of this condition. Consumption of a Mediterranean diet (MedDiet) has been proposed to reduce dementia risk. However, current evidence is inconclusive and is typically derived from small cohorts with limited dementia cases. Additionally, few studies have explored the interaction between diet and genetic risk of dementia.

METHODS

We used Cox proportional hazard regression models to explore the associations between MedDiet adherence, defined using two different scores (Mediterranean Diet Adherence Screener [MEDAS] continuous and Mediterranean diet Pyramid [PYRAMID] scores), and incident all-cause dementia risk in 60,298 participants from UK Biobank, followed for an average 9.1 years. The interaction between diet and polygenic risk for dementia was also tested.

RESULTS

Higher MedDiet adherence was associated with lower dementia risk (MEDAS continuous: HR = 0.77, 95% CI = 0.65-0.91; PYRAMID: HR = 0.86, 95% CI = 0.73-1.02 for highest versus lowest tertiles). There was no significant interaction between MedDiet adherence defined by the MEDAS continuous and PYRAMID scores and polygenic risk for dementia.

CONCLUSIONS

Higher adherence to a MedDiet was associated with lower dementia risk, independent of genetic risk, underlining the importance of diet in dementia prevention interventions.

The impact of Allied Health Professionals on the primary and secondary prevention of obesity in young children: A scoping review

Allied Health Professionals (AHPs) have the capacity to promote healthy behaviours in young children through routine 'contact points', as well as structured weight management programmes. This scoping review aims to evaluate the impact of AHPs in the prevention of obesity in young children. Databases were searched for relevant evidence between 1st January 2000 and 17th January 2022. Eligibility criteria included primary evidence (including, but not limited to; randomized controlled trials, observational studies, service evaluations) evaluating the impact of AHPs on the primary and secondary prevention of obesity in young children (mean age under 5 years old). AHP-related interventions typically demonstrated improvements in outcomes such as nutritional behaviour (e.g. lower sweetened drink intake), with some reductions in screen time. However, changes in weight outcomes (e.g. body mass index (BMI) z-score, BMI) in response to an AHP intervention were inconsistent. There was insufficient data to determine moderating effects, however tentative evidence suggests that those with a lower socioeconomic status or living in an underprivileged area may be more likely to lose weight following an AHP intervention. There was no evidence identified evaluating how AHPs use routine 'contact points' in the prevention of obesity in young children. AHP interventions could be effective in optimizing weight and nutritional outcomes in young children. However, more research is required to determine how routine AHP contact points, across the range of professional groups may be used in the prevention of obesity in young children.

Effects of partial penectomy for penile cancer on sexual function: A systematic review

Penile cancer is a rare but debilitating condition, which often requires aggressive treatment. Partial penectomy is considered as a treatment option when a sufficient portion of the penile shaft can be maintained to preserve functionality. This systematic review, which followed the PRIMSA guidelines, aimed to evaluate the effects of partial penectomy for penile cancer on sexual function—the maintenance of which is often a priority in patient groups—and to identify potential factors which may moderate these effects. A systematic search of PubMed, The Cochrane Library, and Open Grey as well as MEDLINE, CINAHL and Open Dissertations via EBSCOhost was conducted from inception through to 24^th March, 2022. Studies were required to include adults aged ≥18 years who had undergone partial penectomy for the treatment of penile cancer, with a quantitative measure of sexual function available pre- and post-surgery. Four eligible articles were identified for inclusion in this review, three of which reported a decrease in sexual function pre- to post-surgery across all domains of the International Index of Erectile Function (IIEF) questionnaire (erectile function, orgasmic function, sexual desire, intercourse satisfaction and overall satisfaction). Conversely, one study reported an increase in sexual function across IIEF domains, except for orgasmic function, which decreased, pre- to post-surgery. Greater penile length was associated with higher post-operative sexual function, whilst increasing age and higher anxiety levels were associated with lower post-operative sexual function levels in one study. Despite the overall drop in sexual function, many patients were still able to maintain satisfactory sex lives following partial penectomy. Given the limited research in this area and small sample sizes across studies, additional well-controlled investigations are warranted to provide further evidence on the effects of partial penectomy for penile cancer on sexual function.

How is the NHS Low-Calorie Diet Programme expected to produce behavioural change to support diabetes remission: An examination of underpinning theory

Background: In 2020, the National Health Service Low-Calorie Diet Programme (NHS-LCD) was launched, piloting a total diet (TDR) replacement intervention with behaviour change support for people living with Type 2 Diabetes (T2D) and excess weight. Four independent service providers were commissioned to design and deliver theoretically grounded programmes in localities across England. Aims: 1) to develop a logic model detailing how the NHS-LCD programme is expected to produce changes in health behaviour, and (2) to analyse and evaluate the use of behaviour change theory in providers’ NHS-LCD Programme designs. Methods: A documentary review was conducted. Information was extracted from the NHS-LCD service specification documents on how the programme expected to produce outcomes. The Theory Coding Scheme (TCS) was used to analyse theory use in providers’ programme design documents. Results: The NHS-LCD logic model included techniques aimed at enhancing positive outcome expectations of programme participation and beliefs about social approval of behaviour change, to facilitate programme uptake and behaviour change intentions. This was followed by techniques aimed at shaping knowledge and enhancing the ability of participants to self-regulate their health behaviours, alongside a supportive social environment and person-centred approach. Application and type of behaviour change theory within service providers’ programme designs varied. One provider explicitly linked theory to programme content; two providers linked 63% and 70% of intervention techniques to theory; and there was limited underpinning theory identified in the programme design documents for one of the providers. Conclusion: The nature and extent of theory use underpinning the NHS-LCD varied greatly amongst service providers, with some but not all intervention techniques explicitly linked to theory. How this relates to outcomes across providers should be evaluated. It is recommended that explicit theory use in programme design and evidence of its implementation becomes a requirement of future NHS commissioning processes.

A systematic review: Role of dietary supplements on markers of exercise-associated gut damage and permeability

Nutrition strategies and supplements may have a role to play in diminishing exercise associated gastrointestinal cell damage and permeability. The aim of this systematic review was to determine the influence of dietary supplements on markers of exercise-induced gut endothelial cell damage and/or permeability. Five databases were searched through to February 2021. Studies were selected that evaluated indirect markers of gut endothelial cell damage and permeability in response to exercise with and without a specified supplement, including with and without water. Acute and chronic supplementation protocols were included. Twenty-seven studies were included. The studies investigated a wide range of supplements including bovine colostrum, glutamine, probiotics, supplemental carbohydrate and protein, nitrate or nitrate precursors and water across a variety of endurance exercise protocols. The majority of studies using bovine colostrum and glutamine demonstrated a reduction in selected markers of gut cell damage and permeability compared to placebo conditions. Carbohydrate intake before and during exercise and maintaining euhydration may partially mitigate gut damage and permeability but coincide with other performance nutrition strategies. Single strain probiotic strains showed some positive findings, but the results are likely strain, dosage and duration specific. Bovine colostrum, glutamine, carbohydrate supplementation and maintaining euhydration may reduce exercise-associated endothelial damage and improve gut permeability. In spite of a large heterogeneity across the selected studies, appropriate inclusion of different nutrition strategies could mitigate the initial phases of gastrointestinal cell disturbances in athletes associated with exercise. However, research is needed to clarify if this will contribute to improved athlete gastrointestinal and performance outcomes.

Effects of a mediterranean diet on the gut microbiota and microbial metabolites: A systematic review of randomized controlled trials and observational studies

Consumption of the Mediterranean dietary pattern (MedDiet) is associated with reduced risk of numerous non-communicable diseases. Modulation of the composition and metabolism of the gut microbiota represents a potential mechanism through which the MedDiet elicits these effects. We conducted a systematic literature search (Prospero registration: CRD42020168977) using PubMed, The Cochrane Library, MEDLINE, SPORTDiscuss, Scopus and CINAHL databases for randomized controlled trials (RCTs) and observational studies exploring the impact of a MedDiet on gut microbiota composition (i.e., relative abundance of bacteria or diversity metrics) and metabolites (e.g., short chain fatty acids). Seventeen RCTs and 17 observational studies were eligible for inclusion in this review. Risk of bias across the studies was mixed but mainly identified as low and unclear. Overall, RCTs and observational studies provided no clear evidence of a consistent effect of a MedDiet on composition or metabolism of the gut microbiota. These findings may be related to the diverse methods across studies (e.g., MedDiet classification and analytical techniques), cohort characteristics, and variable quality of studies. Further, well-designed studies are warranted to advance understanding of the potential effects of the MedDiet using more detailed examination of microbiota and microbial metabolites with reference to emerging characteristics of a healthy gut microbiome.

Mediterranean diet and the hallmarks of ageing

Ageing is a multifactorial process associated with reduced function and increased risk of morbidity and mortality. Recently, nine cellular and molecular hallmarks of ageing have been identified, which characterise the ageing process, and collectively, may be key determinants of the ageing trajectory. These include genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion and altered intercellular communication. Healthier dietary patterns reduce the risk of age-related diseases and increase longevity and may influence positively one or more of these hallmarks. The Mediterranean dietary pattern (MedDiet) is a plant-based eating pattern that was typical of countries such as Greece, Spain, and Italy pre-globalisation of the food system and which is associated with better health during ageing. Here we review the potential effects of a MedDiet on each of the nine hallmarks of ageing, and provide evidence that the MedDiet as a whole, or individual elements of this dietary pattern, may influence each hallmark positively-effects which may contribute to the beneficial effects of this dietary pattern on age-related disease risk and longevity. We also highlight potential avenues for future research.

Effects of a Mediterranean diet on blood pressure: a systematic review and meta-analysis of randomized controlled trials and observational studies

OBJECTIVE

To conduct a systematic review and meta-analysis investigating effects of MedDiet on blood pressure in randomized controlled trials (RCTs) and associations of MedDiet with risk of hypertension in observational studies.

METHODS

PubMed, The Cochrane Library and EBSCOhost were searched from inception until January 2020 for studies that met the following criteria: participants aged at least 18 years, RCTs investigating effects of a MedDiet versus control on BP, observational studies exploring associations between MedDiet adherence and risk of hypertension. Random-effects meta-analyses were conducted. Meta-regression and subgroup analyses were performed for RCTs to identify potential effect moderators.

RESULTS

Nineteen RCTs reporting data on 4137 participants and 16 observational studies reporting data on 59 001 participants were included in the meta-analysis. MedDiet interventions reduced SBP and DBP by a mean -1.4 mmHg (95% CI: -2.40 to -0.39 mmHg, P = 0.007, I2 = 53.5%, Q = 44.7, τ2 = 1.65, df = 19) and -1.5 mmHg (95% CI: -2.74 to -0.32 mmHg, P = 0.013, I2 = 71.5%, Q = 51.6, τ2 = 4.72, df = 19) versus control, respectively. Meta-regression revealed that longer study duration and higher baseline SBP was associated with a greater decrease in BP, in response to a MedDiet (P < 0.05). In observational studies, odds of developing hypertension were 13% lower with higher versus lower MedDiet adherence (95% CI: 0.78--0.98, P = 0.017, I2 = 69.6%, Q = 41.1, τ2 = 0.03, df = 17).

CONCLUSION

Data suggest that MedDiet is an effective dietary strategy to aid BP control, which may contribute towards the lower risk of CVD reported with this dietary pattern. This study was registered with PROSPERO: CRD42019125073.

The Effects of Exercise on Indirect Markers of Gut Damage and Permeability: A Systematic Review and Meta-analysis

AIM

Exercise appears to cause damage to the endothelial lining of the human gastrointestinal tract and elicit a significant increase in gut permeability.

OBJECTIVE

The aim of this review was to determine the effect of an acute bout of exercise on gut damage and permeability outcomes in healthy populations using a meta-analysis.

METHODS

PubMed, The Cochrane Library as well as MEDLINE, SPORTDiscus and CINHAL, via EBSCOhost were searched through February 2019. Studies were selected that evaluated urinary (ratio of disaccharide/monosaccharide excretion) or plasma markers [intestinal Fatty Acid Binding Protein (i-FABP)] of gut permeability and gut cell damage in response to a single bout of exercise.

RESULTS

A total of 34 studies were included. A random-effects meta-analysis was performed, and showed a large and moderate effect size for markers of gut damage (i-FABP) (ES 0.81; 95% CI 0.63-0.98; n = 26; p < 0.001) and gut permeability (Disaccharide Sugar/Monosaccharide Sugar) (ES 0.70; 95% CI 0.29-1.11; n = 17; p < 0.001), respectively. Exercise performed in hot conditions (> 23 °C) further increased markers of gut damage compared with thermoneutral conditions [ES 1.06 (95% CI 0.88-1.23) vs. 0.66 (95% CI 0.43-0.89); p < 0.001]. Exercise duration did not have any significant effect on gut damage or permeability outcomes.

CONCLUSIONS

These findings demonstrate that a single bout of exercise increases gut damage and gut permeability in healthy participants, with gut damage being exacerbated in hot environments. Further investigation into nutritional strategies to minimise gut damage and permeability after exercise is required. PROSPERO database number (CRD42018086339).

Illness and infection in elite full-contact football-code sports: A systematic review

OBJECTIVES

Full-contact football-code team sports offer a unique environment for illness risk. During training and match-play, players are exposed to high-intensity collisions which may result in skin-on-skin abrasions and transfer of bodily fluids. Understanding the incidence of all illnesses and infections and what impact they cause to time-loss from training and competition is important to improve athlete care within these sports. This review aimed to systematically report, quantify and compare the type, incidence, prevalence and count of illnesses across full-contact football-code team sports.

DESIGN/METHODS

A systematic search of Cochrane Library, MEDLINE, SPORTDiscus, PsycINFO and CINAHL electronic databases was performed from inception to October 2019; keywords relating to illness, athletes and epidemiology were used. Studies were excluded if they did not quantify illness or infection, involve elite athletes, investigate full-contact football-code sports or were review articles.

RESULTS

Twenty-eight studies met the eligibility criteria. Five different football-codes were reported: American football (n=10), Australian rules football (n=3), rugby league (n=2), rugby sevens (n=3) and rugby union (n=9). One multi-sport study included both American football and rugby union. Full-contact football-code athletes are most commonly affected by respiratory system illnesses. There is a distinct lack of consensus of illness monitoring methodology.

CONCLUSIONS

Full-contact football-code team sport athletes are most commonly affected by respiratory system illnesses. Due to various monitoring methodologies, illness incidence could only be compared between studies that used matching incidence exposure measures. High-quality illness surveillance data collection is an essential component to undertake effective and targeted illness prevention in athletes.

Differences in circulating appetite-related hormone concentrations between younger and older adults: a systematic review and meta-analysis

Ageing is associated with reduced appetite and energy intakes. However, the mechanisms underlying this phenomenon are not fully understood. This systematic review and meta-analysis quantified differences in circulating concentrations of appetite-related hormones between healthy older and younger adults. Six databases were searched through 12th June 2018 for studies that compared appetite-related hormone concentrations between older and younger adults. Data were pooled using random-effects meta-analysis and are presented as standardised mean difference (Hedges’ g) with 95% confidence intervals (95% CI). Thirty-five studies were included involving 710 older adults (mean ± SD; age: 73 ± 5 years) and 713 younger adults (age: 28 ± 7 years). Compared with younger adults, older adults exhibited higher fasted and postprandial concentrations of the anorectic hormones cholecystokinin (Fasted: SMD 0.41 (95% CI 0.24, 0.57); p < 0.001. Postprandial: SMD 0.41 (0.20, 0.62); p < 0.001), leptin [Fasted: SMD 1.23 (0.15, 2.30); p = 0.025. Postprandial: SMD 0.62 (0.23, 1.01); p = 0.002] and insulin [Fasted: SMD 0.24 (− 0.02, 0.50); p = 0.073. Postprandial: SMD 0.16 (0.01, 0.32); p = 0.043]. Higher postprandial concentrations of peptide-YY were also observed in older adults compared with younger adults [SMD 0.31 (− 0.03, 0.65); p = 0.075]. Compared with younger adults, older adults had lower energy intakes [SMD − 0.98 (− 1.74, − 0.22); p = 0.011], and lower hunger perceptions in the fasted [SMD − 1.00 (− 1.54, − 0.46); p < 0.001] and postprandial states [SMD − 0.31, (− 0.64, 0.02); p = 0.064]. Higher circulating concentrations of insulin, leptin, cholecystokinin and peptide-YY accord with reduced appetite and energy intakes in healthy older adults. Interventions to reduce circulating levels of these hormones may be beneficial for combatting the anorexia of ageing.

Appetite and energy intake responses to breakfast consumption and carbohydrate supplementation in hypoxia

PURPOSE

The purpose of experiment one was to determine the appetite, acylated ghrelin and energy intake response to breakfast consumption and omission in hypoxia and normoxia. Experiment two aimed to determine the appetite, acylated ghrelin and energy intake response to carbohydrate supplementation after both breakfast consumption and omission in hypoxia.

METHODS

In experiment one, twelve participants rested and exercised once after breakfast consumption and once after omission in normobaric hypoxia (4300 m: F_iO₂ ~11.7%) and normoxia. In experiment two, eleven participants rested and exercised in normobaric hypoxia (4300 m: F_iO₂ ~11.7%), twice after consuming a high carbohydrate breakfast and twice after breakfast omission. Participants consumed both a carbohydrate (1.2g·min^-1 glucose) and a placebo beverage after breakfast consumption and omission. Measures of appetite perceptions and acylated ghrelin were taken at regular intervals throughout both experiments and an ad-libitum meal was provided post-exercise to quantify energy intake.

RESULTS

Breakfast consumption had no significant effect on post exercise energy intake or acylated ghrelin concentrations, despite reductions in appetite perceptions. As such, breakfast consumption increased total trial energy intake compared with breakfast omission in hypoxia (7136 ± 2047 kJ vs. 5412 ± 1652 kJ; p = 0.02) and normoxia (9276 ± 3058 vs. 6654 ± 2091 kJ; p < 0.01). Carbohydrate supplementation had no effect on appetite perceptions or acylated ghrelin concentrations after breakfast consumption or omission. As such, carbohydrate supplementation increased total energy intake after breakfast consumption (10222 ± 2831 kJ vs. 7695 ± 1970 kJ p < 0.01) and omission (8058 ± 2574 kJ vs. 6174 ± 2222 kJ p = 0.02).

CONCLUSION

Both breakfast consumption and carbohydrate supplementation provide beneficial dietary interventions for increasing energy intake in hypoxic conditions.

Response: Commentary on the effects of hypoxia on energy substrate use during exercise

BACKGROUND

A recent commentary has been published on our meta-analysis, which investigated substrate oxidation during exercise matched for relative intensities in hypoxia compared with normoxia. Within this commentary, the authors proposed that exercise matched for absolute intensities in hypoxia compared with normoxia, should have been included within the analysis, as this model provides a more suitable experimental design when considering nutritional interventions in hypoxia.

MAIN BODY

Within this response, we provide a rationale for the use of exercise matched for relative intensities in hypoxia compared with normoxia. Specifically, we argue that this model provides a physiological stimulus replicable of real world situations, by reducing the absolute workload undertaken in hypoxia. Further, the use of exercise matched for relative intensities isolates the metabolic response to hypoxia, rather than the increased relative exercise intensity experienced in hypoxia when utilising exercise matched for absolute intensities. In addition, we also report previously unpublished data analysed at the time of the original meta-analysis, assessing substrate oxidation during exercise matched for absolute intensities in hypoxia compared with normoxia.

CONCLUSION

An increased reliance on carbohydrate oxidation was observed during exercise matched for absolute intensities in hypoxia compared with normoxia. These data now provide a comparable dataset for the use of researchers and practitioners alike in the design of nutritional interventions for relevant populations.

Substrate oxidation and the influence of breakfast in normobaric hypoxia and normoxia

PURPOSE

Previous research has reported inconsistent effects of hypoxia on substrate oxidation, which may be due to differences in methodological design, such as pre-exercise nutritional status and exercise intensity. This study investigated the effect of breakfast consumption on substrate oxidation at varying exercise intensities in normobaric hypoxia compared with normoxia.

METHODS

Twelve participants rested and exercised once after breakfast consumption and once after omission in normobaric hypoxia (4300 m: F_iO₂ ~ 11.7%) and normoxia. Exercise consisted of walking for 20 min at 40%, 50% and 60% of altitude-specific [Formula: see text]O_2max at 10-15% gradient with a 10 kg backpack. Indirect calorimetry was used to calculate carbohydrate and fat oxidation.

RESULTS

The relative contribution of carbohydrate oxidation to energy expenditure was significantly reduced in hypoxia compared with normoxia during exercise after breakfast omission at 40% (22.4 ± 17.5% vs. 38.5 ± 15.5%, p = 0.03) and 60% [Formula: see text]O_2max (35.4 ± 12.4 vs. 50.1 ± 17.6%, p = 0.03), with a trend observed at 50% [Formula: see text]O_2max (23.6 ± 17.9% vs. 38.1 ± 17.0%, p = 0.07). The relative contribution of carbohydrate oxidation to energy expenditure was not significantly different in hypoxia compared with normoxia during exercise after breakfast consumption at 40% (42.4 ± 15.7% vs. 48.5 ± 13.3%, p = 0.99), 50% (43.1 ± 11.7% vs. 47.1 ± 14.0%, p = 0.99) and 60% [Formula: see text]O_2max (54.6 ± 17.8% vs. 55.1 ± 15.0%, p = 0.99).

CONCLUSIONS

Relative carbohydrate oxidation was significantly reduced in hypoxia compared with normoxia during exercise after breakfast omission but not during exercise after breakfast consumption. This response remained consistent with increasing exercise intensities. These findings may explain some of the disparity in the literature.

Towards UK poSt Arthroplasty Follow-up rEcommendations (UK SAFE): protocol for an evaluation of the requirements for arthroplasty follow-up, and the production of consensus-based recommendations

INTRODUCTION

Hip and knee arthroplasties have revolutionised the management of degenerative joint diseases and, due to an ageing population, are becoming increasingly common. Follow-up of joint prostheses is to identify problems in symptomatic or asymptomatic patients due to infection, osteolysis, bone loss or potential periprosthetic fracture, enabling timely intervention to prevent catastrophic failure at a later date. Early revision is usually more straight-forward surgically and less traumatic for the patient. However, routine long-term follow-up is costly and requires considerable clinical time. Therefore, some centres in the UK have curtailed this aspect of primary hip and knee arthroplasty services, doing so without an evidence base that such disinvestment is clinically or cost-effective.

METHODS

Given the timeline from joint replacement to revision, conducting a randomised controlled trial (RCT) to determine potential consequences of disinvestment in hip and knee arthroplasty follow-up is not feasible. Furthermore, the low revision rates of modern prostheses, less than 10% at 10 years, would necessitate thousands of patients to adequately power such a study. The huge variation in follow-up practice across the UK also limits the generalisability of an RCT. This study will therefore use a mixed-methods approach to examine the requirements for arthroplasty follow-up and produce evidence-based and consensus-based recommendations as to how, when and on whom follow-up should be conducted. Four interconnected work packages will be completed: (1) a systematic literature review; (2a) analysis of routinely collected National Health Service data from five national data sets to understand when and which patients present for revision surgery; (2b) prospective data regarding how patients currently present for revision surgery; (3) economic modelling to simulate long-term costs and quality-adjusted life years associated with different follow-up care models and (4) a Delphi-consensus process, involving all stakeholders, to develop a policy document which includes a stratification algorithm to determine appropriate follow-up care for an individual patient.

ETHICS AND DISSEMINATION

Favourable ethical opinion has been obtained for WP2a (RO-HES) (220520) and WP2B (220316) from the National Research Ethics Committee. Following advice from the Confidentiality Advisory Group (17/CAG/0122), data controllers for the data sets used in WP2a (RO-HES) - NHS Digital and The Phoenix Partnership - confirmed that Section 251 support was not required as no identifiable data was flowing into or out of these parties. Application for approval of WP2a (RO-HES) from the Independent Group Advising on the Release of Data (IGARD) at NHS Digital is in progress (DARS-NIC-147997). Section 251 support (17/CAG/0030) and NHS Digital approval (DARS-NIC-172121-G0Z1H-v0.11) have been obtained for WP2a (NJR-HES-PROMS). ISAC (11_050MnA2R2) approval has been obtained for WP2a (CPRD-HES).

The effects of environmental hypoxia on substrate utilisation during exercise: a meta-analysis

Background

A better understanding of hypoxia-induced changes in substrate utilisation can facilitate the development of nutritional strategies for mountaineers, military personnel and athletes during exposure to altitude. However, reported metabolic responses are currently divergent. As such, this systematic review and meta-analysis aims to determine the changes in substrate utilisation during exercise in hypoxia compared with normoxia and identify study characteristics responsible for the heterogeneity in findings.

Methods

A total of six databases (PubMed, the Cochrane Library, MEDLINE, SPORTDiscus, PsychINFO, and CINAHL via EBSCOhost) were searched for published original studies, conference proceedings, abstracts, dissertations and theses. Studies were included if they evaluated respiratory exchange ratio (RER) and/or carbohydrate or fat oxidation during steady state exercise matched for relative intensities in normoxia and hypoxia (normobaric or hypobaric). A random-effects meta-analysis was performed on outcome variables. Meta-regression analysis was performed to investigate potential sources of heterogeneity.

Results

In total, 18 studies were included in the meta-analysis. There was no significant change in RER during exercise matched for relative exercise intensities in hypoxia, compared with normoxia (mean difference: 0.01, 95% CI: -0.02 to 0.05; n = 31, p = 0.45). Meta-regression analysis suggests that consumption of a pre-exercise meal (p < 0.01) and a higher exercise intensity (p = 0.04) when exposed to hypoxia may increase carbohydrate oxidation compared with normoxia.

Conclusions

Exposure to hypoxia did not induce a consistent change in the relative contribution of carbohydrate or fat to the total energy yield during exercise matched for relative intensities, compared with normoxia. The direction of these responses appears to be mediated by the consumption of a pre-exercise meal and exercise intensity.

Electronic supplementary material

The online version of this article (10.1186/s12970-019-0277-8) contains supplementary material, which is available to authorized users.

Are professional young rugby league players eating enough? Energy intake, expenditure and balance during a pre-season

Due to the unique energetic demands of professional young collision sport athletes, accurate assessment of energy balance is required. Consequently, this is the first study to simultaneously investigate the energy intake, expenditure and balance of professional young rugby league players across a pre-season period. The total energy expenditure of six professional young male rugby league players was measured via doubly labelled water over a fourteen-day assessment period. Resting metabolic rate was measured and physical activity level calculated. Dietary intake was reported via Snap-N-Send over a non-consecutive ten-day assessment period, alongside changes in fasted body mass and hydration status. Accordingly, energy balance was inferred. The mean (standard deviation) difference between total energy intake (16.73 (1.32) MJ^.day^-1) and total energy expenditure (18.36 (3.05) MJ^.day^-1) measured over the non-consecutive ten-day period was unclear (-1.63 (1.73) MJ^.day^-1; ES = 0.91 ± 1.28; p = 0.221). This corresponded in a most likely trivial decrease in body mass (-0.65 (0.78) kg; ES = 0.04 ± 0.03; p = 0.097). Resting metabolic rate and physical activity level across the fourteen-day pre-season period was 11.20 (2.16) MJ^.day^-1 and 1.7 (0.2), respectively. For the first time, this study utilises gold standard assessment techniques to elucidate the distinctly large energy expenditures of professional young rugby league players across a pre-season period, emphasising a requirement for equally large energy intakes to achieve targeted body mass and composition adaptations. Accordingly, it is imperative that practitioners regularly assess the energy balance of professional young collision-sport athletes to ensure their unique energetic requirements are achieved.

How well do activity monitors estimate energy expenditure? A systematic review and meta-analysis of the validity of current technologies

OBJECTIVE

To determine the accuracy of wrist and arm-worn activity monitors' estimates of energy expenditure (EE).

DATA SOURCES

SportDISCUS (EBSCOHost), PubMed, MEDLINE (Ovid), PsycINFO (EBSCOHost), Embase (Ovid) and CINAHL (EBSCOHost).

DESIGN

A random effects meta-analysis was performed to evaluate the difference in EE estimates between activity monitors and criterion measurements. Moderator analyses were conducted to determine the benefit of additional sensors and to compare the accuracy of devices used for research purposes with commercially available devices.

ELIGIBILITY CRITERIA

We included studies validating EE estimates from wrist-worn or arm-worn activity monitors against criterion measures (indirect calorimetry, room calorimeters and doubly labelled water) in healthy adult populations.

RESULTS

60 studies (104 effect sizes) were included in the meta-analysis. Devices showed variable accuracy depending on activity type. Large and significant heterogeneity was observed for many devices (I² >75%). Combining heart rate or heat sensing technology with accelerometry decreased the error in most activity types. Research-grade devices were statistically more accurate for comparisons of total EE but less accurate than commercial devices during ambulatory activity and sedentary tasks.

CONCLUSIONS

EE estimates from wrist and arm-worn devices differ in accuracy depending on activity type. Addition of physiological sensors improves estimates of EE, and research-grade devices are superior for total EE. These data highlight the need to improve estimates of EE from wearable devices, and one way this can be achieved is with the addition of heart rate to accelerometry.

PROSPEROREGISTRATION NUMBER

CRD42018085016.

Omega-3 polyunsaturated fatty acids favourably modulate cardiometabolic biomarkers in type 2 diabetes: a meta-analysis and meta-regression of randomized controlled trials

BACKGROUND

Randomized controlled trials (RCTs) suggest that supplementation with omega-3 polyunsaturated fatty acids (n-3PUFAs) may favourably modify cardiometabolic biomarkers in type 2 diabetes (T2DM). Previous meta-analyses are limited by insufficient sample sizes and omission of meta-regression techniques, and a large number of RCTs have subsequently been published since the last comprehensive meta-analysis. Updated information regarding the impact of dosage, duration or an interaction between these two factors is therefore warranted. The objective was to comprehensively assess the effect of n-3PUFAs supplementation on cardiometabolic biomarkers including lipid profiles, inflammatory parameters, blood pressure, and indices of glycaemic control, in people with T2DM, and identify whether treatment dosage, duration or an interaction thereof modify these effects.

METHODS

Databases including PubMed and MEDLINE were searched until 13th July 2017 for RCTs investigating the effect of n-3PUFAs supplementation on lipid profiles, inflammatory parameters, blood pressure, and indices of glycaemic control. Data were pooled using random-effects meta-analysis and presented as standardised mean difference (Hedges g) with 95% confidence intervals (95% CI). Meta-regression analysis was performed to investigate the effects of duration of supplementation and total dosage of n-3PUFAs as moderator variables where appropriate.

RESULTS

A total of 45 RCTs were identified, involving 2674 people with T2DM. n-3PUFAs supplementation was associated with significant reductions in LDL [ES: - 0.10, (95% CI - 0.17, - 0.03); p = 0.007], VLDL (ES: - 0.26 (- 0.51, - 0.01); p = 0.044], triglycerides (ES: - 0.39 (- 0.55, - 0.24; p ≤ 0.001] and HbA1c (ES: - 0.27 (- 0.48, - 0.06); p = 0.010]. Moreover, n-3PUFAs supplementation was associated with reduction in plasma levels of TNF-α [ES: - 0.59 (- 1.17, - 0.01); p = 0.045] and IL-6 (ES: - 1.67 (- 3.14, - 0.20); p = 0.026]. All other lipid markers, indices of glycaemic control, inflammatory parameters, and blood pressure remained unchanged (p > 0.05).

CONCLUSIONS

n-3PUFAs supplementation produces favourable hypolipidemic effects, a reduction in pro-inflammatory cytokine levels and improvement in glycaemia. Neither duration nor dosage appear to explain the observed heterogeneity in response to n-3PUFAs. Trial registration This trial was registered at http://www.crd.york.ac.uk as CRD42016050802.

Collision activity during training increases total energy expenditure measured via doubly labelled water

PURPOSE

Collision sports are characterised by frequent high-intensity collisions that induce substantial muscle damage, potentially increasing the energetic cost of recovery. Therefore, this study investigated the energetic cost of collision-based activity for the first time across any sport.

METHODS

Using a randomised crossover design, six professional young male rugby league players completed two different 5-day pre-season training microcycles. Players completed either a collision (COLL; 20 competitive one-on-one collisions) or non-collision (nCOLL; matched for kinematic demands, excluding collisions) training session on the first day of each microcycle, exactly 7 days apart. All remaining training sessions were matched and did not involve any collision-based activity. Total energy expenditure was measured using doubly labelled water, the literature gold standard.

RESULTS

Collisions resulted in a very likely higher (4.96 ± 0.97 MJ; ES = 0.30 ± 0.07; p = 0.0021) total energy expenditure across the 5-day COLL training microcycle (95.07 ± 16.66 MJ) compared with the nCOLL training microcycle (90.34 ± 16.97 MJ). The COLL training session also resulted in a very likely higher (200 ± 102 AU; ES = 1.43 ± 0.74; p = 0.007) session rating of perceived exertion and a very likely greater (- 14.6 ± 3.3%; ES = - 1.60 ± 0.51; p = 0.002) decrease in wellbeing 24 h later.

CONCLUSIONS

A single collision training session considerably increased total energy expenditure. This may explain the large energy expenditures of collision-sport athletes, which appear to exceed kinematic training and match demands. These findings suggest fuelling professional collision-sport athletes appropriately for the "muscle damage caused" alongside the kinematic "work required".

The Effect of Sex on Heart Rate Variability at High Altitude

There is evidence suggesting that high altitude (HA) exposure leads to a fall in heart rate variability (HRV) that is linked to the development of acute mountain sickness (AMS). The effects of sex on changes in HRV at HA and its relationship to AMS are unknown.

METHODS

HRV (5-min single-lead ECG) was measured in 63 healthy adults (41 men and 22 women) 18-56 yr of age at sea level (SL) and during a HA trek at 3619, 4600, and 5140 m, respectively. The main effects of altitude (SL, 3619 m, 4600 m, and 5140 m) and sex (men vs women) and their potential interaction were assessed using a factorial repeated-measures ANOVA. Logistic regression analyses were performed to assess the ability of HRV to predict AMS.

RESULTS

Men and women were of similar age (31.2 ± 9.3 vs 31.7 ± 7.5 yr), ethnicity, and body and mass index. There was main effect for altitude on heart rate, SD of normal-to-normal (NN) intervals (SDNN), root mean square of successive differences (RMSSD), number of pairs of successive NN differing by >50 ms (NN50), NN50/total number of NN, very low-frequency power, low-frequency (LF) power, high-frequency (HF) power, and total power (TP). The most consistent effect on post hoc analysis was reduction in these HRV measures between 3619 and 5140 m at HA. Heart rate was significantly lower and SDNN, RMSSD, LF power, HF power, and TP were higher in men compared with women at HA. There was no interaction between sex and altitude for any of the HRV indices measured. HRV was not predictive of AMS development.

CONCLUSIONS

Increasing HA leads to a reduction in HRV. Significant differences between men and women emerge at HA. HRV was not predictive of AMS.

Changes in appetite, energy intake, body composition, and circulating ghrelin constituents during an incremental trekking ascent to high altitude

Purpose

Circulating acylated ghrelin concentrations are associated with altitude-induced anorexia in laboratory environments, but have never been measured at terrestrial altitude. This study examined time course changes in appetite, energy intake, body composition, and ghrelin constituents during a high-altitude trek.

Methods

Twelve participants [age: 28(4) years, BMI 23.0(2.1) kg m⁻²] completed a 14-day trek in the Himalayas. Energy intake, appetite perceptions, body composition, and circulating acylated, des-acylated, and total ghrelin concentrations were assessed at baseline (113 m, 12 days prior to departure) and at three fixed research camps during the trek (3619 m, day 7; 4600 m, day 10; 5140 m, day 12).

Results

Relative to baseline, energy intake was lower at 3619 m (P = 0.038) and 5140 m (P = 0.016) and tended to be lower at 4600 m (P = 0.056). Appetite perceptions were lower at 5140 m (P = 0.027) compared with baseline. Acylated ghrelin concentrations were lower at 3619 m (P = 0.046) and 4600 m (P = 0.038), and tended to be lower at 5140 m (P = 0.070), compared with baseline. Des-acylated ghrelin concentrations did not significantly change during the trek (P = 0.177). Total ghrelin concentrations decreased from baseline to 4600 m (P = 0.045). Skinfold thickness was lower at all points during the trek compared with baseline (P ≤ 0.001) and calf girth decreased incrementally during the trek (P = 0.010).

Conclusions

Changes in plasma acylated and total ghrelin concentrations may contribute to the suppression of appetite and energy intake at altitude, but differences in the time course of these responses suggest that additional factors are also involved. Interventions are required to maintain appetite and energy balance during trekking at terrestrial altitudes.

Effects of Dietary Nitrate Supplementation on Physiological Responses, Cognitive Function, and Exercise Performance at Moderate and Very-High Simulated Altitude

Purpose: Nitric oxide (NO) bioavailability is reduced during acute altitude exposure, contributing toward the decline in physiological and cognitive function in this environment. This study evaluated the effects of nitrate (NO3−) supplementation on NO bioavailability, physiological and cognitive function, and exercise performance at moderate and very-high simulated altitude.

Methods:Ten males (mean (SD): V˙O2max: 60.9 (10.1) ml·kg⁻¹·min⁻¹) rested and performed exercise twice at moderate (~14.0% O₂; ~3,000 m) and twice at very-high (~11.7% O₂; ~4,300 m) simulated altitude. Participants ingested either 140 ml concentrated NO3−-rich (BRJ; ~12.5 mmol NO3−) or NO3−-deplete (PLA; 0.01 mmol NO3−) beetroot juice 2 h before each trial. Participants rested for 45 min in normobaric hypoxia prior to completing an exercise task. Exercise comprised a 45 min walk at 30% V˙O2max and a 3 km time-trial (TT), both conducted on a treadmill at a 10% gradient whilst carrying a 10 kg backpack to simulate altitude hiking. Plasma nitrite concentration ([NO2−]), peripheral oxygen saturation (SpO₂), pulmonary oxygen uptake (V˙O2), muscle and cerebral oxygenation, and cognitive function were measured throughout.

Results: Pre-exercise plasma [NO2−] was significantly elevated in BRJ compared with PLA (p = 0.001). Pulmonary V˙O2 was reduced (p = 0.020), and SpO₂ was elevated (p = 0.005) during steady-state exercise in BRJ compared with PLA, with similar effects at both altitudes. BRJ supplementation enhanced 3 km TT performance relative to PLA by 3.8% [1,653.9 (261.3) vs. 1718.7 (213.0) s] and 4.2% [1,809.8 (262.0) vs. 1,889.1 (203.9) s] at 3,000 and 4,300 m, respectively (p = 0.019). Oxygenation of the gastrocnemius was elevated during the TT consequent to BRJ (p = 0.011). The number of false alarms during the Rapid Visual Information Processing Task tended to be lower with BRJ compared with PLA prior to altitude exposure (p = 0.056). Performance in all other cognitive tasks did not differ significantly between BRJ and PLA at any measurement point (p ≥ 0.141).

Conclusion: This study suggests that BRJ improves physiological function and exercise performance, but not cognitive function, at simulated moderate and very-high altitude.

The effect of moderate versus severe simulated altitude on appetite, gut hormones, energy intake and substrate oxidation in men

Acute exposure to high altitude (>3500 m) is associated with marked changes in appetite regulation and substrate oxidation but the effects of lower altitudes are unclear. This study examined appetite, gut hormone, energy intake and substrate oxidation responses to breakfast ingestion and exercise at simulated moderate and severe altitudes compared with sea-level. Twelve healthy males (mean ± SD; age 30 ± 9years, body mass index 24.4 ± 2.7 kg·m^-2) completed in a randomised crossover order three, 305 min experimental trials at a simulated altitude of 0 m, 2150 m (∼15.8% O₂) and 4300 m (∼11.7% O₂) in a normobaric chamber. Participants entered the chamber at 8am following a 12 h fast. A standardised breakfast was consumed inside the chamber at 1 h. One hour after breakfast, participants performed a 60 min treadmill walk at 50% of relative V˙O_2max. An ad-libitum buffet meal was consumed 1.5 h after exercise. Blood samples were collected prior to altitude exposure and at 60, 135, 195, 240 and 285 min. No trial based differences were observed in any appetite related measure before exercise. Post-exercise area under the curve values for acylated ghrelin, pancreatic polypeptide and composite appetite score were lower (all P < 0.05) at 4300 m compared with sea-level and 2150 m. There were no differences in glucagon-like peptide-1 between conditions (P = 0.895). Mean energy intake was lower at 4300 m (3728 ± 3179 kJ) compared with sea-level (7358 ± 1789 kJ; P = 0.007) and 2150 m (7390 ± 1226 kJ; P = 0.004). Proportional reliance on carbohydrate as a fuel was higher (P = 0.01) before breakfast but lower during (P = 0.02) and after exercise (P = 0.01) at 4300 m compared with sea-level. This study suggests that altitude-induced anorexia and a subsequent reduction in energy intake occurs after exercise during exposure to severe but not moderate simulated altitude. Acylated ghrelin concentrations may contribute to this effect.

Mouth rinsing with a sweet solution increases energy expenditure and decreases appetite during 60 min of self-regulated walking exercise

Carbohydrate mouth rinsing can improve endurance exercise performance and is most ergogenic when exercise is completed in the fasted state. This strategy may also be beneficial to increase exercise capacity and the energy deficit achieved during moderate-intensity exercise relevant to weight control when performed after an overnight fast. Eighteen healthy men (mean (SD); age, 23 (4) years; body mass index, 23.1 (2.4) kg·m^-2) completed a familiarisation trial and 3 experimental trials. After an overnight fast, participants performed 60 min of treadmill walking at a speed that equated to a rating of perceived exertion of 13 ("fairly hard"). Participants manually adjusted the treadmill speed to maintain this exertion. Mouth rinses for the experimental trials contained either a 6.4% maltodextrin solution with sweetener (CHO), a taste-matched placebo (PLA), or water (WAT). Appetite ratings were collected using visual analogue scales and exercise energy expenditure and substrate oxidation were calculated from online gas analysis. Increased walking distance during CHO and PLA induced greater energy expenditure compared with WAT (mean difference (90% confidence interval); 79 (60) kJ, P = 0.035, d = 0.24; and 90 (63) kJ, P = 0.024, d = 0.27, respectively). Appetite area under the curve was lower in CHO and PLA than WAT (8 (6) mm, P = 0.042, d = 0.43; and 6 (8) mm, P = 0.201, d = 0.32, respectively). Carbohydrate oxidation was higher in CHO than PLA and WAT (7.3 (6.7) g, P = 0.078, d = 0.47; and 10.1 (6.5) g, P = 0.015, d = 0.81, respectively). This study provides novel evidence that mouth rinsing with a sweetened solution may promote a greater energy deficit during moderate-exertion walking exercise by increasing energy expenditure and decreasing appetite. A placebo effect may have contributed to these benefits.